The present invention relates to a diagnostic catheter used for various kinds of diagnosis in the state of being inserted in a body cavity or lumen such as a blood vessel, a vas, and a digestive organ, and particularly to a rapid-exchange (RX) type catheter provided at its distal end with a lumen for insertion of a guide wire.
In a blood vessel insertion lumen represented by a catheter for use in Percutaneous Transluminal Coronary Angioplasty (PTCA) (this catheter will hereinafter be referred to as PTCA catheter), a guide wire lumen for insertion of a guide wire is provided over the whole length of the catheter in addition to a working lumen used for treatment or diagnosis.
The guide wire is inserted into the guide wire lumen prior to the insertion of the catheter into a blood vessel, and its distalcend precedes in the blood vessel to guide the distal end of the catheter to the vicinity of the diseased part (angiostenosis portion).
The catheter thus provided with the guide wire lumen over the whole length thereof is called an Over The Wire (OTW) type catheter.
For the PTCA procedure, a variety of catheters such as a dilation catheter, a stent delivery catheter, an atherectomy device, a rotoblator, a medicament injection catheter, an ultrasonic diagnostic catheter, etc. are used. In addition, the kind of catheter, the sizes of the balloon and stent of the dilation catheter, and the method of treatment are selected according to the properties of the angiostenosis portion and the conditions of the patient. Therefore, there are cases where exchange of the catheter is needed after the insertion into a blood vessel. Besides, in the case of setting a plurality of stents, also, the catheter may be drawn away and inserted a few times.
In the case of such an exchange of catheter, generally, it is preferable to keep the guide wire indwelling in the blood vessel, for the purposes of alleviation of burden on the patient, reductions in the operation time and labor, prevention of infection, etc.
In the conventional OTW type catheter, however, the guide wire lumen is provided over the whole length of the catheter as above-mentioned. Therefore, in order to exchange the catheter while keeping the guide wire indwelling in the blood vessel, the guide wire must project to the exterior at least beyond the whole length of the catheter. If the guide wire does not project to the exterior beyond the whole length of the catheter, the guide wire terminates at an intermediate position in the catheter, so that it is impossible to insert the catheter into an organism by operating the guide wire. Where the guide wire projects to the exterior beyond the whole length of the catheter, the guide wire projecting to the exterior is too long, resulting in that the operationality of the catheter is lowered by the guide wire.
As a countermeasure against this problem, there is the rapid-exchange (RX) type catheter provided with a guide wire lumen only at the distal end thereof. The RX type catheter includes a working lumen and a guide wire lumen. The working lumen is provided over the whole length of the catheter, and the guide wire lumen is provided substantially in parallel to the working lumen over a length of several centimeters at the distal end of the catheter. Thus, unlike the OTW type catheter, the RX type catheter is not provided with the guide wire lumen extending over the whole length of the catheter.
Therefore, in the RX type catheter, the guide wire lumen is shorter than that in the OTW type catheter, so that the guide wire need not be projecting to the exterior beyond the whole length of the catheter at the time of exchanging the catheter while keeping the guide wire indwelling in an organism. As a result, the catheter can be exchanged without spoiling the operationality of the catheter.
However, in the conventional RX type catheter, since the guide wire lumen is short, it is difficult for a force of pushing the catheter by the operator to be transmitted to the distal end of the catheter. In many cases, it is difficult for the distal end of the catheter to pass through an angiostenosis portion constituting the diseased part. In such an instance, it has been necessary to exchange the RX type catheter for an OTW type catheter so as to enable passage through the angiostenosis portion.
In addition, for enhancing the pushing force at the distal end of the catheter, it may be contemplated to enlarge the length of the guide wire lumen of the RX type catheter. In this case, however, as the length over which the working lumen and the guide wire lumen are parallel to each other is enlarged, the length of the portion of an increased outside diameter of the catheter is also enlarged accordingly. Thus, it is not preferable to enlarge the length of the guide wire lumen, in consideration of burden on the organism or the like.